1. Field of the Invention
The present invention relates a magnetic sensor capable of detecting a variation of a magnetic field with high sensitivity, and a current sensor capable of detecting a variation of a current flowing through a conductor line with high sensitivity.
2. Description of the Related Art
In measuring correctly a control current which flows into a circuit of control equipment, a method where resistances are connected in series within the circuit to measure a voltage drop of the resistances is applied generally. In this case, however, a load different from the control system is given, and there is a possibility that an adverse influence may be exerted on the control system. Consequently, a method of indirectly measuring a control current by detecting the gradient of a current magnetic field generated by the control current has been used. Specifically, a control current is supplied to a U-shaped, curved conductor line, and variation of current magnetic fields produced around the curved conductor line is detected by use of a Hall device (for example, refer to Japanese Unexamined Patent Publication No.H07-123090).
However, the above-described current sensor has problems that a miniaturization is difficult and that the linearity of detection sensitivity to the change of magnetic field or high-frequency response are inadequate and so on. For this reason, a current sensor, in which a giant magnetoresistive element developing a Giant Magneto-Resistive effect (hereinafter referred to as GMR element) is arranged in a current magnetic field generated by the control current in order to detect its gradient instead of the Hall element, is proposed. That current sensor using such a GMR element can improve the detection sensitivity and high-frequency response, and what is more, a detection characteristic that is stabilized against a temperature change is obtainable.